Repair of wells



May 2 1967 J. s. BOLDRICK ETAL 3,316,963

REPAIR OF WELLS Filed April 27, 1964 wmammwa 2.55.21

INVENTORS. JOHN s. BoLoRlcK,

BY HENRY M- KRAUSE, JR.,

United States Patent litice 3,316,963 Patented May 2, 1967 Houston,Tex., to Esso Production Houston, Tex., a corporation of The presentinvention is directed to repairing a well. More particularly, t-heinvention is concerned with a well operation wherein there has beensubsidence of the ground or movement of the surface casing. In its morespecific Iaspects, the invention is concerned with method and apparatusfor repairing a well.

In the drilling of oil and gas wells, it is common practice to set asu-rface string of pipe which serves to protect shallow fresh watersands from contamination, provides a means for controlling the wellduring the deeper drilling operations, and supports the weight ofsubsequent strings of casing and tubing. If the well is completed, theoil or gas string is set inside this surface pipe. Mostly, the weight ofthe oil or gas string is supported on the wellhead on top of the surfacepipe so that the oil or gas string is in tension and the surface pipe isin compression after the well is completed. Subsequent conditions canand have caused these loads to change. For example, subsidence of thesurface formations can cause the surface pipe to drop. This is resistedby the oil or gas string which is fixed a-t its bottom and rigidlyconnected to the surface pipe at the surface wellhead. The end result isthat the surface pipe stress tends to reverse from compression totension and the stress on the oil or gas string reverses from tension tocompression. These stress reversals can cause serious well problems suchas leakage of thread connections, obstruction to passage of tools, andmay even result in the failure of the casing strings. Heretofore,conditions resulting from earth subsidence and movement of the surfacepipe have been corrected by using a conventional workover rig andkilling the well. The wellhead was then separated and the oil or gasstring pulled into tension, following which the excess oil or gas stringpipe was cut and removed and the wellhead then reconnected.

In accordance with the present invention, problems due to subsidence ofthe earth and surface casing movement may be solved without using aconventional workover rig and without the necessity of removing thewellhead or breaking any of the wellhead seals. Thus, the presentinvention may be briefly described as a method of providing origin-alstress on a well having a wellhead arranged on a surface pipe and havinga pipe string connected to the wellhead wherein original stress on thesurface pipe and pipe st-ring is changed such as to be reversed. Thus,instead of the oil string being `in tension, it is in compression andrather than the surface casing being in compression, it is in tension.Where such a situation arises, in accordance with the present invention,compressive stress is applied to the surface pipe at a point below thewellhead. The surface pipe is then cut and separated between thewellhead and the point where stress is applied and thereafter theseparated surface pipe ends are then sealingly joined whereby originalstress is provided On both the `surface pipe and the pipe string.

In accordance with the present invention, after the surface pipe hasbeen cut and separated, a section of split surface pipe is placedbetween the separated ends of the surface pipe, and then the separatedends and the section are welded together to extend the length of thesurface pipe and to return the surface pipe to compression and the oilstring to tension.

Alter-natively, reduction in compressive loading on surface pipe may beperformed by removing a section of the surface pipe by cutting same andthen pulling the ends of the surface pipe together and then sealinglyjoining them such as by wel-ding. Thus, in accordance with the presentinvention, the condition of changes in original stress may be correctedby employing apparatus which comprises or consists essentially of atleast rst and second piston cylinders having a piston in each of thecylinders with a piston arm extending outwardly from the cylinders. Aplurality of cylinders may be employed and in one operation fourcylinders were actually used. The free end of each of the piston armshas a clamp for releasable connection to the wellhead. The opposite endof the piston cylinder has a hinged clamp which is adapted to be placedaround the surface pipe, the hinged clamp being provided with means formaintaining it around the surface pipe, and with s-lip means forengaging with the surface pipe. By connecting the lclamp on the pistonarms to the wellhead and by placing the hinged clamp around the su-rfacecasing, pressure may then be applied to the piston cylinder in eitherdirection, as desired, to control or alter the relative positions of thehinged clamp and the clamp connected to the pistou arms. With thisassembly installed, in applying pressure to the piston cylinders acompression load may ybe induced between the wellhead and the surfacepipe so that the pipe may be safely cut by any means, such as with acutting torch or by a mechanical cutter. In a tension load on thesurface pipe, an excess of that induced by the piston cylinders istransferred to the piston cylinders when the surface pipe is cut. If, onthe other hand, it is desired to induce tension loads into the oilstring or pipe, iiuid pressure is applied so as to move apart the c-lampattached to the wellhead and the clamp attached to the surface pipeuntil the desired load, as determined by the pressure applied, isobtained.

A split section of -surface pipe may be inserted and aligned in theresulting gap in Ithe surface pipe and welded in place or otherwisejoined to the separated ends to become an integra-l part of the surfacepipe string. When the hinged clamp assembly is released, the compressionload is then carried by the s-urface pipe.

The technique of the present invention may also be used to reducecompressive loading in surface pipe if such should be desired and inthis instance a section of the surface pipe would be removed aftercutting same and pressure applied to pull the separated ends of the pipetogether for rejoining, lsuch as by welding. i

Thus, the present invention is quite useful `and provides a safe andeconomica-l means of correcting reverse surface pipe stress in wellswhere subsidence of the earths surface or movement has caused a reversalor change in loading on lthe surface pipe and oil pipe string.

T-he present invention will be further described by reference to thedrawing in which:

FIG. 1 illustrates the apparatus on the well with the stress of thesurface pipe and oil string reversed;

FiG. 2 is a showing of the well after cutting the surface pipe, raisingthe wellhead and inserting a split section of surface pipe between theseparated ends of the surface pipe; and

FIG. 3 is a showing of the repaired well.

Referring now to the drawing and specifically to FIG. 1, numeral 11designates coacting piston cylinders having a piston 12 arranged thereinattached to a piston arm 13. The free end of piston arm 13 is connectedthrough a yoke 14 and pin 15 to a C-shaped clamp 16 which is providedwith means, such as threaded bolts 17, for attachment t-o flanges 18 onthe wellhead 19. A surface pipe or casing Ztl is also connected to thewellhead 19 and the hinged clamp 21, which is attached by yokes 22 andpins 23 to connecting member 24 and piston cylinder 11. The hinged clamp21 is provided with double slips 25 which bite into the external surfaceof the surface pipe 20. Hinged clamp 21 is also provided with threadedbolts 26 to maintain the hinged clamp 21 around the surface pipe 20, thethreaded bol-ts being arranged in openings of anges 27 on the hingedclamp 21.

It is to be noted that an oil or pipe string 28 is arrangedconcentrically within the surface pipe 20 and a second pipe string 29 isalso arranged concentrically within the oil pipe string 28. Thesestrings are connected to and are sealed with the wellhead 19 andordinarily are suspended therefrom such that the oil string 28 and pipestring 29 are in tension. It is to be noted that the surface pipe orcasing 20 is arranged within the well bore 30 drilled from the earthssurface 31 and cemented in place with cement 32. The oil pipe string 28is fixed at the bottom of the well, such as with a packer, or cementedin the well and is rigidly connected to the surface pipe through thewellhead 19.

In FIG. l, it may be assumed that there has been earth subsidence andthe surface pipe 20 is in tension which, in turn, results in the oilpipe string 28 being in compression rather than the opposite, which isnormally true. Hydraulic pressure is exerted on the pistons 12 throughhydraulic lines 33 and 34 from a source of hydraulic fluid (not shown)as a safety measure. A pressure gauge 35 is connected to hydraulic line33 to register the pressure exerted downwardly on pistons 12. Inaccordance with the present invention, with the apparatus illustrated inplace, the surface casing 20 is cut at a point C below the wellhead 19and between the wellhead and the clamp 21.

The wellhead 19 is then raised, as shown in FIG. 2, by applying force onthe pistons 12 from the opposite direction, as will be described, tocause a separation in the surface pipe 20 and to provide a space 39 forinsertion of a section 40 of split surface pipe in the space 39.

The raising operation is accomplished by injection of hydraulic fluidunder a sufficient pressure from a source (not shown) below the pistons12 through lines 36 and 37, pressure being indicated on pressure gauge38. This provides for separation of the surface casing 20 and provides aspace 39, as has been described, into which the sections 49 of splitsurface pipe may be inserted. With the surface casing in compression andthe oil pipe string in tension, the clamps 16 and 21 may be removedafter the sections 40 have been sealingly joined into the surface pipe20, such as by welding, with welds 41. The well assembly, in itsrepaired condition, with the surface pipe 20 in compression and oilstring 28 in tension, is shown in FIG. 3.

If it is desired to remove a section of the surface pipe 20, stepwisethe procedure would be reversed proceeding from FIG. 3 to FIG. 2 and toFIG. 1, rather than the opposite as has been described. In thisinstance, with the Well in a condition as shown in FIG. 3, the apparatuswould be placed on the well as shown in FIG. 2 and cuts would then bemade on the lines of the welds 41 in FIG. 3 and the section 40- would beremoved as shown in FIG. 2. Then the separated ends of the cut surfacepipe 20 would be pulled together with the apparatus, as described, byapplying uid pressure through lines 33 and 34 against the piston 12. Theltwo ends would then be sealed together by welding at the point C asshown in FIG. 1.

It will be seen from the foregoing description taken with the drawingthat a mode and apparatus have been provided by way of which oil and/ orgas wells may be repaired without requiring the killing of the Well andthe breaking of the wellhead seals; thus, the present invention is quiteadvantageous and useful.

The nature and objects of the present invention having been fullydescribed and illustrated and the best mode and embodiment thereof setforth, what we wish to claim as new and useful and secure by LettersPatent is:

1. A method of providing stress on a well having a Wellhead arranged ona surface pipe and having a pipe string connected to the wellhead andwherein the stress on said surface pipe and pipe string is changed whichcomprises applying stress to said surface pipe at a point below thewellhead, cutting and separating said surface pipe between the wellheadand said point and then sealingly joining the ends of said separatedsurface pipe whereby stress is provided on both said surface pipe andpipe string.

2. A method of providing stress on a well having a wellhead arranged ona surface pipe and having a pipe string connected to the wellhead andwherein the normal stress on said surface pipe and pipe string ischanged which comprises applying stress to said surface pipe at a pointbelow the wellhead, cutting and separating said surface pipe between thewellhead and said point, inserting between the separated ends of saidsurface pipe a section of pipe sufficient to extend the length of saidsurface pipe and to maintain the applied stress, and then sealinglyjoining the ends of said separated surface pipe to said section wherebynormal stress is provided on both said surface pipe and pipe string.

3. A method of providing stress on a well a having a wellhead arrangedon a surface pipe and having a pipe string connected to the wellhead andwherein the stress on said surface pipe and pipe string is changed whichcomprises applying stress to said surface pipe at a point below thewellhead, cutting and separating said surface pipe between the wellheadand said point, removing a section of said cut surface pipe, and thensealingly joining said separated surface pipe after removal of saidsection whereby stress is provided on both said surface pipe and pipestring.

4. A method of providing original stress on a well having a wellheadaranged on a surface pipe and having a pipe string connected to thewellhead and wherein the original stress on said surface pipe and pipestring is changed which comprises applying stress to said surface pipeat a point below the wellhead, cutting and separating said surface pipebetween the wellhead and said point and then welding the ends of saidseparated surface pipe whereby original stress is provided on both saidsurface pipe and pipe string.

5. A method of providing original stress on a well having a wellheadarranged on a surface pipe and having a pipe string connected to thewellhead and wherein the original stresson said surface pipe and pipestring is changed which comprises applying stress to and supporting saidsurface pipe at a point below the wellhead, cutting and separating saidsurface pipe between the wellhead and said point7 sealingly joining saidseparated surface pipe, and releasing support from said surface pipewhereby original stress is provided on both said surface pipe and pipestring.

6. A method of providing stress on a well having a wellhead arranged ona surface pipe and having a pipe string connected to the wellhead andwherein the stress on said surface pipe and pipe string is reversedwhich comprises applying stress to said surface pipe at a point belowthe wellhead, cutting said surface pipe between the wellhead and saidpoint, raising the upper end of said cut surface pipe, inserting betweenthe lower and upper ends of said cut surface pipe a section of pipe ofsufiicient length to extend the length of said surface pipe and tomaintain the applied stress, and then sealingly joining the ends of saidseparated surface pipe to said section whereby the desired stress isprovided on both said surface pipe and pipe string.

7. A method of providing stress on a well having a wellhead arranged ona surface pipe and having a pipe string connected to the wellhead whichcomprises applying stress to said surface pipe at a point below thewellhead, cutting said surface pipe between the wellhead and said point,raising the upper end of said cut surface pipe, removing a section ofsaid cutsurface pipe, lowering the upper end of said surface pipe, andthen sealingly joining the ends of saidseparated surface pipe afterremoval of said section whereby the desired stress is provided on bothsaid surface pipe and pipe string.

References Cited by the Examiner UNITED STATES PATENTS 1,982,835 12/1934Stampi et a1. 254-30 2,126,933 8/1938 Stone et al. 254-29 6 Carruthers61-46.5 Grant et al. 254-93 Hubby 166--75 Brown 166-49 X CHARLES E.OCONNELL, Primary Examiner.

JAMES A. LEP'PINK, Assistant Examiner.

1. A METHOD OF PROVIDING STRESS ON A WELL HAVING A WELLHEAD ARRANGED ONA SURFACE PIPE AND HAVING A PIPE STRING CONNECTED TO THE WELLHEAD ANDWHEREIN THE STRESS ON SAID SURFACE PIPE AND PIPE STRING IS CHANGED WHICHCOMPRISES APPLYING STRESS TO SAID SURFACE PIPE AT A POINT BELOW THEWELLHEAD, CUTTING AND SEPARATING SAID SURFACE PIPE BETWEEN THE WELLHEADAND SAID POINT AND THEN SEALINGLY JOINING THE ENDS OF SAID SEPARATEDSURFACE PIPE WHEREBY STRESS IS PROVIDED ON BOTH SAID SURFACE PIPE ANDPIPE STRING.